The present invention relates to a laminate coated with a radiation-curing printing ink or printing varnish and a process for the production of such a laminate using such a printing varnish or such a printing ink. The invention also relates to a back-filled moulding containing such a laminate as well as a process for the production of such a moulding.
From the prior art, printing inks based on solid resins, in particular polycarbonate, are known, which are typically dissolved in halogen-free solvents. One printing ink of this type, referred to as the generic case, is described by EP 0 688 839 B1 which, in view of the polycarbonate described there, is to be incorporated in the present application as a possible embodiment of the binder belonging to the invention.
This printing ink known from the prior art is disadvantageous, however, in so far as the solvent-containing printing inks known from the prior art tend to dry in the screen by evaporation of the solvent, particularly after a certain down time without printing. This leads to screen blockage and additional cleaning is necessary. In the most unfavourable case, the screen becomes unusable as a result of this. Another disadvantage of this technology known from the prior art consists in the fact that the drying of the printing ink has to take place by hot air in a drying tunnel or oven; this leads to the processing being prolonged by the time necessary for drying and therefore it cannot be optimised as desired. Furthermore, the IR dryers used for thermal drying cause increased space and energy requirements, resulting in increased costs.
Also known from the prior art is a radiation-curing resin which is provided with reactive monomers that are also UV-curing. The associated GB 2 370 279 A describes a radiation-curing polyurethane acrylate with a polycarbonate component in the chemical structure which, however, exhibits disadvantages in processability. Particularly when printing on polycarbonate substrates, the problem of poor adhesion occurs in the so-called back-injection processes, i.e. in the processing technique in which a polycarbonate film printed using the printing ink is then back-injected again with a thermoplastic polymer on the printing side. Because the ink lies in a sandwich between the polycarbonate film and the injection moulded material, no abrasion of the film can take place in daily use. A further disadvantage of this prior art is the adhesion of the printed image to the mould during forming and the high pressure and temperature sensitivity of the printed image, which in turn leads to disadvantageous washout and therefore a poor printed image when back-injected.
The object of the present invention is therefore to create a laminate or a process for the production of a laminate with a printing ink, wherein the adhesion of the printing ink and/or of the printing varnish in relation to the substrate is improved and optimised. In particular, the need to use volatile solvents is ruled out so that undesirable drying in the screen during the printing process is prevented together with the necessary post-thinning with solvent and, as a result, the processing time is reduced. As a result, finer details can be printed and thus a higher print quality can be achieved. In the further processing step of back-injecting, a disadvantageous washout or impairments to the printed image can also be avoided.